Flow control tool

ABSTRACT

A tool for incorporation in a drill string has an outer body (11, 12, 13) and a spool (17, 18, 19) rotationally and slidably mounted within the body. A cam groove (20) is formed on camming component (17) of the spool and interacts with pins (21) to cause uni-directional spool rotation through a number of pre-set angular positions as the spool is reciprocated. The valving component (18) of the spool is closed internally by wall (26) and has orifices (25) which come into and out of registration with body openings (29) as the spool is moved through its pre-set positions. When in registration, flow into the tool will leave the tool radially outwardly through openings (29); but when out of registration, the flow will be into chamber (28) of body central component (12), and back into the valving component (18) downstream of wall (26) through apertures (27).

This invention relates to a flow control tool for incorporation in anunderground string.

The exploration for and production of oil and gas from undergroundlocations requires the drilling of an elongate bore to an undergroundreservoir. To achieve this, a driven cutting bit is positioned at theleading end of an elongate drilling tube made up from lengths of pipeconnected end-to-end, which drilling tube is referred to in the art as adrill string. As the bore is drilled, it is lined with a casing andsubsequently, following withdrawal of the drill string, a further tubeis inserted into that casing which further tube is also made up fromlengths of pipe connected end-to-end. This further tube is referred toin the art as a production string.

Drilling is performed by pumping a liquid (usually referred to as "mud")along the drill string to cause rotation of the drill bit, to cool andlubricate the drill bit, and to clean cuttings out of the drilled bore.An hydraulic motor driving the cutting bit is located at the forward endof the drill string, upstream of the cutting bit, and is operated by themud pumped from the surface down the string. Upstream of the motor,there is usually located telemetry equipment (known as an MWD unit),powered by a generator driven by the pumped mud and feeding signals backto the surface, concerning various parameters relating to the drilling.

After a period of drilling, it may be necessary to circulate liquid forexample to obtain samples of cuttings, thereby to determine the natureof the formation being cut. To achieve this, mud is pumped down thedrill string, returning cuttings back to the surface. The life of boththe generator for the telemetry equipment and the hydraulic motor forthe cutting bits depends upon the operational circulating time and so itis desirable to cease operation of both of these, other than when actualdrilling is to be performed. There is therefore a need for a by-passvalve arrangement in the drill string upstream of the hydraulic motorand telemetry equipment, whereby operation of both may be suspendedother than when actual drilling is taking place.

In some circumstances, there is a need for a by-pass valve which allowsdual flow, wherein part of the flow is circulated, by-passing thehydraulic motor and telemetry equipment, with a reduced flow through thevalve to the motor and so on. This has the advantage that the motor willstill rotate but at a lower rate in view of the reduced flow, soreducing the likelihood of the bit becoming stuck in the bare hole.

After drilling has been completed, but before production is commenced,there is a cased-hole clean-out phase which may employ a principalstring of one diameter and at the far end thereof a further, shortstring of a smaller diameter. Whilst cleaning the main casing, it isadvantageous to use very high flow rates for the clean-out fluid, butthe presence of the further short string restricts that to some extent,due to friction pressure losses. It would therefore be advantageous forthe clean-out fluid flow to by-pass the further short string until thelowermost part of the bore is to be cleaned out by that string.

There have been various proposals for so-called circulating tools forincorporation in a string, to allow fluid pumped from the surface toissue through the string wall in the region of the tool and so toby-pass equipment downstream of the tool, or to constrain that fluid tocontinue along the string from the tool. In one such proposal, a valveis operated by dropping into the string a weight which is carried by thefluid flow to the tool and which then changes the state of the valve.Such a tool may be operated only a limited number of times, andtypically three or four.

Another proposal is to provide a tool which is operated by axialpressure thereon, caused by the weight of the string above the tool.However, this can subject equipment downstream of the tool to high axialloads and moreover often cannot be used in the case of a bore extendingsignificantly out of vertical. Yet another proposal is to be found inU.S. Pat. No. 4,298,077. In this, the repeated application and removalfluid pressure may sequentially move a valve member between one positionwhere there can be no recirculating flow to another position whereparallel flow paths, both for recirculating flow and through the motor,are possible. Though this may extend the life for example of a down-holemotor, the high pressures usually applied for example with clean-outfluid ensures that there will still be some flow through the motorduring all operations, so shortening the useful operational lifethereof.

The present invention aims at providing a circulating tool suitable forincorporation in an underground string and which may be operated betweentwo different states an indefinite number of times, selectively whenrequired.

According to the present invention, there is provided a flow controltool for incorporation in an underground string, comprising an elongatehollow outer body, a hollow inner spool mounted within the outer bodyand movable both axially and rotationally with respect thereto, motioncontrol means arranged between the body and the spool to effect rotationof the spool relative to the body sequentially through a plurality ofpre-set angularly spaced positions upon axial reciprocation of thespool, at least one spool orifice extending through a side wall thereofand which comes into communication with an opening through the body at afirst pre-set position of the spool and is out of communication at asecond pre-set position, spring means urging the spool in the axialdirection opposed to the pumped fluid flow direction to a third pre-setposition where flow through the spool is closed off, and the spool beingarranged such that fluid under pressure and flowing axially therethroughmoves the spool axially against the action of the spring.

It will be appreciated that in the present invention, the tool isactuated by relieving the pressure of the fluid pumped along the string,so allowing the spool to be moved under the action of the spring means,in the axial direction against the fluid flow. The motion control meanscauses the spool to turn relative to the body, whereby on subsequentlypumping fluid along the string, the spool orifice will be incommunication with the body opening, or will be out of communicationwith the body opening, depending upon the state of the tool prior torelieving the pressure. Conveniently, the spool orifice and body openingcome into communication by direct registration therebetween, when thespool is in a first pre-set position.

Preferably, the motion control means comprises a cam surface on one ofthe spool and the body, and a cam follower on the other of the spool andthe body. Conveniently, the cam surface is on a cylindrical surface ofthe spool and comprises a camming groove in which is located a pin on aconfronting surface of the body. The motion control means may effectuni-directional rotation of the spool with respect to the body uponreciprocation of the spool and may define at least one first pre-setposition and at least one second pre-set position, spaced both axiallyand angularly from each other. Advantageously, there are two first andtwo second pre-set positions, arranged alternately, though there couldbe other numbers of such pre-set positions.

In a preferred embodiment, the spool is disposed nearer the downstreamend of a string to which the tool is coupled, when in its second pre-setposition. To allow flow then to continue through the tool, the spool mayhave an internal dividing wall downstream of the or each orificetherein, and at least one flow re-entry aperture leading to the interiorof the spool downstream of said wall, the body defining an internalchamber with which both the or each spool orifice and the or each spoolaperture communicate when the spool is in a second pre-set position. Inthis way, the flow will be through the spool orifice to enter the bodychamber, and then back into the spool downstream of said dividing wallthrough the re-entry aperture, to continue down the spool and thenaxially out of the body. Conversely, when the spool is in its firstpre-set position, the dividing wall prevents flow continuing along thespool so that all flow will pass out of the tool through the or eachregistering spool orifice and body opening.

In a modified form of the tool as described, flow passages may beprovided to permit partial flow through the tool and partial outwardflow through a communicating spool orifice and body opening, when thespool is set to the first pre-set position.

The axially opposed ends of the body may be provided with anyconventional form of string coupler, to allow the body to form a part ofthe string itself. Thus, the body should have an external diameter notgreater than the external diameter of the pipe connections making up thestring.

By way of example only, one specific embodiment of circulating tool ofthis invention will now be described in detail, reference being made tothe accompanying drawings, in which:

FIGS. 1A and 1B together are a sectional view through the tool in athrough-flow (second) pre-set position, line X--X marked on both Figureslying in a common plane;

FIG. 2 is a sectional view, on a reduced scale, through the tool but ina circulating (first) pre-set position;

FIG. 3 is a sectional view through the tool in a non-pressured position;and

FIG. 4 is a developed view of the camming groove of the spool andshowing at Y--Y the line of section of FIGS. 1 to 3.

The tool shown in the drawings comprises a cylindrical body 10 made upfrom upstream, central and downstream components 11, 12 and 13 rigidlyand sealingly connected end-to-end. The free ends of the upstream anddownstream components 11 and 13 are formed with female and male stringcouplers 14 and 15 respectively, to allow the body to be connected intoand form a part of a drill string. Slidably and rotationally mountedwithin the body 10 is a spool 16, constructed from camming, valving andforward components 17, 18 and 19 rigidly and sealing connectedend-to-end.

The camming component 17 has a cam groove 20 formed therein, the 360°developed profile of which is shown in FIG. 4. A pair of diametricallyopposed pins 21 are mounted in upstream component 11 of the body andengage in the cam groove 20, to cause the spool to perform a definedmotion with respect to the body upon axial reciprocation of the spool.The profile is such that the rotation of the spool will beuni-directional and when moved nearer the downstream end of the tool,the pins will be located in portions 22 or 23 of the groove 20,corresponding to the positions illustrated in FIGS. 1 and 2respectively. Conversely, each time the spool is moved towards theupstream end of the tool, the pins will be located in a diametricallyopposed pair of portions 24 of the groove.

The valving component 18 of the spool has four equi-spaced orifices 25and, immediately downstream thereof, a internal dividing wall 26.Downstream of that wall, there are nine flow re-entry apertures 27. Thecentral component 12 of the body defines a chamber 28, with which theorifices 25 and apertures 27 communicate, when the spool 16 is in theposition illustrated in FIG. 1--that is, with the pins 21 in portions 22of camming groove 20.

The central component 12 of the body also defines four openings 29, withwhich the orifices 25 register when the spool 16 is in the positionillustrated in FIG. 2--that is, with the pins 21 in portions 23 ofcamming groove 20. Here, the dividing wall 26 prevents flow towards thedownstream end of the tool.

A compression spring 33 is located in annular space 30, between thedownstream component 13 of the body and downstream component 19 of thespool. That spring could be a helical spring or a disc spring and actsbetween the downstream end face 31 of the valving component 18 and ashoulder 32 of downstream component 13 of the body, so urging the spooltowards the upstream end of the tool, to the position illustrated inFIG. 3--that is, with the pins 21 in portions 24 of camming groove 20.

The upstream component 11 of the body has four pressure relieving bores34 communicating with a space downstream of the camming component 17.This ensures that the pressure below the camming component is thatprevailing externally of the tool which always will be less than thepressure at the upstream end of the tool, within the string wheneverfluid is being pumped along the string.

In use, the tool is fitted into a string so that the body 10 forms apart thereof. Initially, the spool 16 is in the position illustrated inFIG. 3, by virtue of the action of the compression spring 33. Then, onpumping fluid along the string 33, the differential pressure to whichthe camming component 17 is subjected will move the spool 16 axiallydownstream. Depending upon which portions 24 of the camming groove 20were located the pins 21, the spool will then move axially until thepins 21 are located in portion 22 (so allowing flow axially through thetool) or in portions 23 (so allowing circulation of fluid, out of thetool). Each time a change of state is required, the pressure of thepumped fluid is relieved, so allowing the spool 16 to move under theaction of the compression spring back to its FIG. 3 position and then onpumping fluid once more, the spool will move to its other pre-setposition.

The tool may be operated an indefinite number of times to change thecirculation state, merely by relieving the pressure of the pumped fluidand then restoring that pressure. Provided that the pumped pressure isabove the minimum required to move the spool against the action of thecompression spring, the change of state will occur. Moreover, thesurface pump pressure will indicate whether there has been a change ofstate, as there will be increased pump pressure due to increasedfrictional losses if the mud is circulating through the telemetry systemand the mud motor. For cased-hole liner clean-out operations, theincreased pump pressure would be as a result of the reduced bore of theliner clean-out drill string.

In addition to the advantages noted above, the use of a tool of thisinvention allows use of an increased mud flow rate during circulatingoperations, so reducing the mud circulation time and increasing thedisplacement and removal efficiency of the cuttings. There is also anincreased motor life, should these higher flow rates be employed, sincenot all the mud has to pass through the motor.

A further advantage of having a tool of this invention located upstreamof a drill motor and MWD (telemetry) unit is that the tool may isolatethe motor and MWD unit from damage when using lost circulation material(LCM) to spot an area where losses are occurring. In turn this increasesthe life and reliability of the motor and MWD unit.

An alternative use for the tool is in a coiled tubing applicationemploying downhole motors. While coiled tubing is being run into a hole,it is necessary to circulate fluid (typically nitrogen) through thetubing. As coiled tubing does not possess significant collapseresistance, the differential pressure between the well bore and thecoiled tubing must be minimised by increasing the pressure within thetubing. This can be achieved by percolating fluid out of the end of thetubing, to ensure the pressure at the end of the tubing approximatelymatches the well bore pressure.

If a downhole motor is connected to the end of the coiled tubing, it ishighly desirable that the fluid flow bypasses the motor whilst thepercolation is in a progress. This is because the process of running thetubing can take many hours, which would otherwise reduce the usefulmotor life. The tool of this invention may thus be installed upstream ofthe motor, in order that circulation may be through the tool, soby-passing the motor and conserving the motor life.

We claim:
 1. A flow control tool for incorporation in an undergroundstring, comprising an elongate hollow outer body having first and secondaxial ends, a hollow inner spool mounted within the outer body andmovable both axially and rotationally with respect thereto, motioncontrol means arranged between the body and the spool to effect rotationof the spool relative to the body sequentially through a plurality ofpre-set angularly spaced positions upon axial reciprocation of thespool, at least one spool orifice extending through a side wall thereofand which comes into communication with an opening through the body at afirst pre-set position of the spool and is out of communication at asecond pre-set position, an internal dividing wall within the spooldownstream of the at least one spool orifice, at least one flow re-entryaperture leading to the interior of the spool downstream of said wall,an internal chamber within the body and with which both the at least onespool orifice and the at least one re-entry aperture communicate whenthe spool is in the second pre-set position whereby fluid flow may beessentially axially through the tool, spring means urging the spool inthe axial direction opposed to the pumped fluid flow direction to athird pre-set position where flow through the spool is closed off, andthe spool being arranged such that fluid under pressure and flowingaxially therethrough moves the spool axially against the action of thespring.
 2. A flow control tool as claimed in claim 1, wherein flowpassages are provided to permit partial flow through the tool andpartial outward flow through a communicating spool orifice and bodyopening, when the spool is set to the first pre-set position.
 3. A flowcontrol tool as claimed in claim 1, wherein the motion control meanscomprises a cam surface on one of the spool and the body, and a camfollower on the other of the spool and the body.
 4. A flow control toolas claimed in claim 3, wherein the cam surface comprises a camminggroove formed in a cylindrical surface of one of the spool and body. 5.A flow control tool as claimed in claim 4, wherein the cam followercomprises a pin mounted on a cylindrical surface of the other of thespool and body and confronting said surface in which is formed thecamming groove.
 6. A flow control tool as claimed in claim 4, whereinthe camming groove defines at least one first and one second pre-setpositions spaced both axially and angularly from each other.
 7. A flowcontrol tool is claimed in claim 4, wherein the camming groove definestwo first and two second pre-set positions arranged alternately.
 8. Aflow control tool as claimed in claim 4, wherein there are fourequi-spaced spool orifices and four corresponding body openings.
 9. Aflow control tool as claimed in claim 1, wherein the motion controlmeans is arranged to effect uni-directional rotation of the spool withrespect to the body upon reciprocation of the spool.
 10. A flow controltool as claimed in claim 1, wherein the or each spool orifice comes intoand out of direct registration with a respective body opening by axialdisplacement of the spool between its first and second pre-setpositions.
 11. A flow control tool as claimed in claim 1, wherein thetwo axial ends of the hollow body are provided with string couplers,whereby the body may form a part of a string.
 12. A flow control tool asclaimed in claim 1, wherein an annular chamber is formed between thebody and the spool downstream of the at least one spool orifice, whichchamber is provided with pressure-relieving bores whereby the spool maymove against the force of the spring solely under the influence ofsufficient applied fluid pressure.
 13. A flow control tool forincorporation in an underground string, comprising an elongate hollowouter body, a hollow inner spool mounted within the outer body andmovable both axially and rotationally with respect thereto, motioncontrol means arranged between the body and the spool to effect rotationof the spool relative to the body sequentially through a plurality ofpre-set angularly spaced positions upon axial reciprocation of thespool, at least one spool orifice extending through a side wall thereofand which comes into communication with said opening at a second pre-setposition, an internal dividing wall downstream of the at least oneorifice therein, the spool and body together defining a chambertherebetween downstream of the body opening and with which chamber theat least one spool orifice communicates when the spool is in its secondpre-set position so that fluid flowing axially into the body leaves thespool through the at least one spool orifice to flow into the chamberand from there flows axially along the tool to the downstream endthereof, spring means urging the spool in the axial direction opposed tothe pumped fluid flow direction, and the spool being arranged such thatfluid under pressure and flowing axially therethrough moves the spoolaxially against the action of the spring.
 14. A flow control tool asclaimed in claim 13, wherein the motion control means comprises a camsurface on one of the spool and the body, and a cam follower on theother of the spool and the body.
 15. A flow control tool as claimed inclaim 10, wherein the cam surface comprises a camming groove formed in acylindrical surface of one of the spool and body, and the cam followercomprises a pin mounted on a cylindrical surface of the other of thespool and body and confronting said surface in which is formed thecamming groove.
 16. A flow control tool as claimed in claim 15, whereinthe camming groove defines two first and two second pre-set positionsarranged alternately and space both axially and angularly from eachother.
 17. A flow control tool as claimed in claim 16, wherein themotion control means is arranged to effect unidirectional rotational ofthe spool with respect to the body upon reciprocation of the spool. 18.A flow control tool as claimed in claim 13, wherein an annular chamberis formed between the body and the spool downstream of the at least onespool orifice, which chamber is provided with pressure-relieving boreswhereby the spool may move against the force of the spring solely underthe influence of sufficient applied fluid pressure.